Methods for producing a high protein corn meal from a whole stillage byproduct and system therefore

ABSTRACT

The present invention relates generally to corn dry-milling, and more specifically, to methods for producing a high protein corn meal from a whole stillage byproduct produced in a corn dry-milling process for making ethanol and a system therefore. In one embodiment, a method for producing a high protein corn meal from a whole stillage byproduct includes, in a corn dry-milling process for making ethanol, separating the whole stillage byproduct into an insoluble solids portion and a thin stillage portion. The thin stillage portion is separated into a protein portion and a water soluble solids portion. Next, the protein portion is dewatered then dried to define a high protein corn meal that includes at least 40 wt % protein on a dry basis.

TECHNICAL FIELD

The present invention relates generally to corn dry-milling, and morespecifically, to methods for producing a high protein corn meal from awhole stillage byproduct produced in a corn dry-milling process formaking ethanol and a system therefore.

BACKGROUND

Wet mill corn processing plants convert corn grain into severaldifferent co-products, such as germ (for oil extraction), gluten feed(high fiber animal feed), gluten meal (high protein animal feed), andstarch-based products, including ethanol, high fructose corn syrup, orfood and industrial starch. However, because constructing wet-millingplants is complex and capital-intensive, almost all new plants builttoday are dry mill plants.

Dry milling plants generally convert corn into only two products, i.e.,ethanol and distiller's grains with solubles. A typical corn dry millprocess consists of four major steps: grain handling and milling,liquefaction and saccharification, fermentation, and co-productrecovery. Grain handling and milling is the step in which the corn isbrought into the plant and ground to promote better starch to glucoseconversion. Liquefaction and saccharification is where the starch isconverted into glucose. Fermentation is the process of yeast convertingglucose into ethanol. Co-product recovery is the step in which theethanol and corn by-products are purified and made market ready.

The recovery of ethanol and co-products generally begins with the beerbeing sent to a distillation system. With distillation, ethanol istypically separated from the rest of the beer through a set of stepwisevaporizations and condensations. The beer less the alcohol extractedthrough distillation is known as whole stillage, which contains a slurryof the spent grains including corn protein, fiber, oil, and sugars. Butthese byproducts are too diluted to be of much value at this point andare further processed to provide the distiller's grains with soluble.

In typical processing, when the whole stillage leaves the distillationcolumn, it is generally subjected to a decanter centrifuge to separateinsoluble solids or “wet cake”, which includes fiber, from the liquid or“thin stillage”, which includes, e.g., proteins and oil. Afterseparation, the thin stillage moves to evaporators to boil awaymoisture, leaving a thick syrup that contains the soluble (dissolved)solids. The concentrated syrup is typically mixed with the wet cake, andthe mixture may be sold to beef and dairy feedlots as distillers wetgrain with solubles (DWGS). Alternatively, the wet cake and concentratedsyrup mixture may be dried in a drying process and sold as distillersdried grain with solubles (DDGS). The resulting DDGS generally has acrude protein content of about 29% and is an especially useful feed forcattle and other ruminants due to its by-pass protein content.

While DDGS and DWGS provide a critical secondary revenue stream thatoffsets a portion of the overall ethanol production cost, it would bebeneficial to provide a method and system where a higher protein cornproduct can be obtained from the whole stillage to be sold at a highercost per ton than DDGS or DWGS.

SUMMARY OF THE INVENTION

The present invention is directed to a method for producing a highprotein corn meal from a whole stillage byproduct produced in a corndry-milling process for making ethanol and a system therefore.

In one embodiment, a method for producing a high protein corn meal froma whole stillage byproduct includes, in a corn dry-milling process formaking ethanol, separating the whole stillage byproduct into aninsoluble solids portion and a thin stillage portion. The thin stillageportion is separated into a protein portion and a water soluble solidsportion. Then, the protein portion is dewatered and dried to define ahigh protein corn meal that includes at least 40 wt % protein on a drybasis.

In another embodiment, a method for producing a high protein corn mealfrom a whole stillage byproduct includes, in a corn dry-milling processfor making ethanol, subjecting the whole stillage byproduct to afiltration centrifuge, a decanter centrifuge, a pressure screen, or apaddle screen to separate the whole stillage into an insoluble solidsportion and a thin stillage portion. The thin stillage is next subjectedto a nozzle centrifuge or a cyclone apparatus to separate the thinstillage portion into a protein portion and a water soluble solidsportion. Next, the protein portion is subjected to a decanter centrifugeto dewater the protein portion then the dewatered protein portion isdried to define a high protein corn meal that includes at least 40 wt %protein on a dry basis.

In yet another embodiment, a system for producing high protein corn mealfrom a whole stillage byproduct produced via a corn dry-milling processincludes a first apparatus selected from a filtration centrifuge, adecanter centrifuge, a pressure screen, or a paddle screen to separatethe whole stillage into an insoluble solids portion and a thin stillageportion. A second apparatus is provided that is selected from a nozzlecentrifuge or a cyclone apparatus to separate the thin stillage portioninto a protein portion and a water soluble solids portion. The systemfurther includes a decanter centrifuge for dewatering the proteinportion, and a drying apparatus that dries the dewatered protein portionso as to yield a high protein corn meal, which includes at least 40 wt %protein on a dry basis.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description of the embodiments given below, serve toexplain the principles of the invention.

FIG. 1 is a flow diagram of a prior art dry-milling process and systemfor producing ethanol and distiller's grains with solubles;

FIG. 2 is a flow diagram of a method and system for producing a highprotein corn meal from a whole stillage byproduct produced via a corndry-milling process for making ethanol in accordance with an embodimentof the invention;

FIG. 3 is a cross-sectional view of a filtration centrifuge inaccordance with one embodiment of the invention;

FIG. 4 is a cross-sectional view of the inner housing or basket shown inthe filtration centrifuge of FIG. 3;

FIG. 5 is cross-sectional view of the conveyor shown in the filtrationcentrifuge of FIG. 3;

FIG. 6 is an enlarged view of a portion of the filtration centrifugeshown in FIG. 3;

FIG. 7 is an enlarged view of a portion of the filtration centrifugeshown in FIG. 3 illustrating the pre-concentration zone;

FIG. 8 is an enlarged view of a portion of the filtration centrifugeshown in FIG. 3 illustrating the first washing zone;

FIG. 9 is an enlarged view of a portion of the filtration centrifugeshown in FIG. 3 illustrating the second washing zone; and

FIG. 10 is a cross-sectional view of a filtration centrifuge inaccordance with another embodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

FIG. 1 is a flow diagram of a prior art corn dry milling process forproducing ethanol, such process is fully discussed in U.S. Pat. No.7,101,691, entitled “Alcohol Production Using Sonication”, which isexpressly incorporated by reference herein in its entirety. Asignificant portion of ethanol in the United States is produced from drymilling processes, which convert corn into two products, namely ethanoland distiller's grains with solubles. And although virtually any typeand quality of grain can be used to produce ethanol, the feedstock forthis process is typically corn referred to as “No. 2 Yellow Dent Corn.”

With specific reference to FIG. 1, a typical corn dry milling process 10begins with a milling step 12 in which dried whole corn kernels arepassed through hammer mills to grind them into meal or a fine powder.The ground meal is mixed with water to create a slurry, and a commercialenzyme such as alpha-amylase is added. This slurry is then heated in apressurized jet cooking process 14 to solubilize the starch in theground meal. This is followed by a liquefaction step 16 at which pointadditional alpha-amylase may be added. The alpha-amylase hydrolyzes thegelatinized starch into maltodextrins and oligosaccharides to produce aliquefied mash or slurry.

This can be followed by separate saccharification and fermentationsteps, 18 and 20, respectively, although in most commercial dry millethanol processes, saccharification and fermentation occursimultaneously. In the saccharification step 18, the liquefied mash iscooled and a commercial enzyme such as gluco-amylase is added tohydrolyze the maltodextrins and short-chained oligosaccharides intosingle glucose sugar molecules. In the fermentation step 20, a commonstrain of yeast (Saccharomyces cerevisae) is added to metabolize theglucose sugars into ethanol and CO2. Upon completion, the fermentationmash (“beer”) will contain about 17% to 18% ethanol (volume/volumebasis), plus soluble and insoluble solids from all the remaining graincomponents, including fiber, protein, and oil, for example. Yeast canoptionally be recycled in a yeast recycling step 22. In some instancesthe CO2 is recovered and sold as a commodity product.

Subsequent to the fermentation step 20 is a distillation and dehydrationstep 24 in which the beer is pumped into distillation columns where itis boiled to vaporize the ethanol. The ethanol vapor is condensed in thedistillation columns, and liquid alcohol (in this instance, ethanol)exits the top of the distillation columns at about 95% purity (190proof). The 190 proof ethanol then goes through a molecular sievedehydration column, which removes the remaining residual water from theethanol, to yield a final product of essentially 100% ethanol (199.5proof).

Finally, a centrifugation step 26 involves centrifuging, via a decantercentrifuge, the residuals or whole stillage leftover from distillationso as to separate the insoluble solids portion or “wet cake”, whichincludes fiber, from the liquid portion or “thin stillage” portion,which includes protein, oil, etc. Next, the thin stillage portion entersevaporators in an evaporation step 28 in order to boil away moisturethereby leaving a thick syrup, which contains the soluble (dissolved)solids as well as protein and oil. This concentrated syrup is typicallyreferred to as corn condensed distillers soluble and is mixed with thecentrifuged wet cake then sold to beef and dairy feedlots as distillerswet grain with solubles (DWGS). The wet cake and concentrated syrupmixture may be further dried in a drying step 30 and sold as distillersdried grain with solubles (DDGS) to dairy and beef feedlots. Thedistiller's grains with solubles co-product provides a criticalsecondary revenue stream that offsets a portion of the overall ethanolproduction cost.

In accordance with the present invention, FIG. 2 schematicallyillustrates an embodiment of a method and system for producing a highprotein corn meal, collectively numeral 32, from the whole stillagebyproduct produced in a typical corn dry-milling process 10 like thatjust described in FIG. 1. Again, the whole stillage byproduct contains aslurry of soluble and insoluble solids, i.e., the spent grains from thedistillation and dehydration step 24, which includes protein, fiber,oil, and sugars that are processed in accordance with embodiments ofthis invention to produce a high protein corn meal that can be sold,e.g., as pig and chicken feed, at a higher cost per ton than typicalDDGS or DWGS. In one embodiment, the resulting high protein corn mealincludes at least 40 wt % protein on a dry basis as compared to aprotein content of about 29% typically found in DDGS.

With further reference to FIG. 2, the whole stillage byproduct can bepiped from the typical corn dry mill distillation and dehydration step24 and subjected to an optional paddle screen 34. The optional paddlescreen 34 is situated before a filtration centrifuge 40, which isfurther discussed below, so as to aid ultimately in separation of theinsoluble solids portion, e.g., fiber, from the thin stillage portion byinitially filtering out desirable amounts of water and protein and,incidentally, small fiber fines from the whole stillage byproduct. Thisinitial screening can help reduce the resulting load on the subsequentfiltration centrifuge 40. The resulting underflow from the paddle screen34 eventually joins with the thin stillage underflow from the filtrationcentrifuge 40, as will be discussed in greater detail below.

To filter the whole stillage byproduct, the optional paddle screen 34can include screen openings of no greater than about 150 microns. Inanother example, the paddle screen 34 can include openings therein of nogreater than about 100 microns. In yet another example, the openingstherein are no greater than about 50 microns. It should be understoodthat these values are exemplary and that those of ordinary skill in theart will recognize how to determine the size of the openings to achievethe desired filtration. In one example, the optional paddle screen 34 isa standard type paddle screen as is known in the art. One such suitablepaddle screen 34 is the FQ-PS32 available from Fluid-Quip, Inc. ofSpringfield, Ohio. It should be understood that the optional paddlescreen 34 may be replaced with other types of pre-concentration devices,e.g., a standard pressure screen or conic centrifuge, which can performthe desired filtration or preconcentration function. One such suitablepressure screen is the PS-Triple available from Fluid-Quip, Inc. ofSpringfield, Ohio.

With reference now to FIGS. 3-10, these figures illustrate embodimentsof the filtration centrifuge 40 whereat the whole stillage byproduct isseparated into the insoluble solids portion, which includes fiber, andthe thin stillage portion, which includes protein, oil, etc. One suchsuitable filtration centrifuge is described in U.S. patent applicationSer. No. 12/435,451 entitled “Apparatus and Method for Filtering aMaterial from a Liquid Medium”, and filed May 5, 2009, the contents ofwhich is expressly incorporated by reference herein in its entirety. Asbest shown in FIG. 3, the filtration centrifuge 40 is a single,self-contained device that may be configured to perform both the initialfiltering (sometimes referred to as a pre-concentration) of the wholestillage byproduct and washing of the fiber so as to clean the fiber andremove protein and other components that remain associated with thefiber after the initial filtration or pre-concentration.

The washing of the fiber may include a washing cycle, wherein the fiberis mixed and rinsed in wash water, followed by a de-watering cycle,wherein the wash water is separated from the fiber. The washing of thefiber may include multiple rinsing/de-watering cycles. Additionally, acounter current washing technique may be employed to save wash waterusage. After washing the fiber, but before the fiber exits thecentrifuge, the fiber may go through an enhanced de-watering stage, acompaction stage, and/or an air dry stage to further de-water or dry thefiber. This may save the dryer capacity or eliminate the dryeraltogether. In reference to FIG. 3, and in one exemplary embodiment, thefiltration centrifuge 40 includes an outer housing 42, a generallytubular inner housing or basket 44 (filtration screen) substantiallydisposed in the interior of outer housing 42, a conveyor 46 generallycoaxially disposed in the basket 44, and a plurality of conduit lines 48generally coaxially disposed in conveyor 46 and adapted to receive theslurry, i.e., whole stillage byproduct, and wash water therethrough.

The outer housing 42 includes a first end wall 50, a second end wall 52opposite and spaced from the first end wall 50, and at least one sidewall 54 connecting the first and second end walls 50, 52 so as to definean interior 56. The outer housing 42 may have any suitable shape. Forexample, in one embodiment, the outer housing 42 may be generallyrectangular including an upper side wall portion 54 a, a lower side wallportion 54 b, and a pair of lateral side wall portions 54 c (one shownin FIG. 3) extending therebetween. The use of descriptive terms upper,lower, and lateral for the side walls 54 are used to facilitate thedescription of the filtration centrifuge 40 and should not be construedto limit the centrifuge 40 to any particular orientation. As shown inFIG. 3, the lower side wall portion 54 b may include a plurality ofpanels that collectively define one or more (three shown in FIG. 3)funnel-shaped hoppers 60 a, 60 b, 60 c, each hopper having acorresponding outlet 62 a, 62 b, 62 c. As discussed in more detailbelow, a multi-hopper configuration provides for collection of theslurry (minus the fiber) in the pre-concentration stage and the washwater in the washing stages (and from the wash water in the enhancedde-watering stage and compaction stage if such stages are utilized). Themulti-hopper configuration also provides for a counter current washwater technique to be utilized.

The outer housing 42 further includes one or more interior panels 64that generally compartmentalize the filtration centrifuge 40 into aplurality of zones 66. For example, and as explained in more detailbelow, the panels 64 may generally define a pre-concentration zone 66 aand one or more washing zones 66 b, 66 c (two shown in FIG. 3). Althoughtwo washing zones are illustrated in FIG. 3, those of ordinary skill inthe art will appreciate that the number of washing zones may beapplication specific. For example, in the corn dry mill processdescribed above, it is contemplated that between one and six washingzones, and preferably between two and four washing zones, may beincluded in the filtration centrifuge 40. More zones, however, areconsidered to be within the scope of the invention. In addition to theabove panels 64 and corresponding zones 66, an interior panel 68adjacent the second end 52 of the outer housing 42 also defines an exitchute 70 including an outlet 72 for receiving the filtered and washedmaterial (e.g., fiber) processed by filtration centrifuge 40.

As mentioned above, and as illustrated in FIGS. 3 and 4, the basket 44is disposed in the interior 56 of outer housing 42 and includes a firstend 74 defined by a first hub 76, a second end 78 defined by a secondhub 80, and at least one side wall 82 extending between the first andsecond ends 74, 78 and coupled to the first and second hubs 76, 80.While the basket 44 may have any suitable shape, in one embodiment, thebasket 44 may be generally cylindrical and have a generally circularcross-sectional shape characterized by a basket diameter Db. In oneembodiment, the basket diameter Db may be substantially constant alongthe length of the basket 44 (e.g., right circular cylinder) (not shown).

In another embodiment, however, the basket diameter Db may vary along atleast one or more portions of the length Lb of the basket 44. By way ofexample, and as shown in FIG. 4, the basket 44 may include a firstbasket section 86 adjacent the first end 74 of the basket 44. The firstbasket section 86 includes a generally outwardly tapered (i.e.,diverging) or cone-shaped configuration in a direction from first end 74toward second end 78. The first basket section 86 may be followed by asecond basket section 88 generally configured as a right circularcylinder. The first basket section 86 (e.g., the conical-shaped section)may extend between 0%-100% of the length of the basket 44. In oneembodiment, however, the first basket section 86 extends for about 10%to about 30% of the length Lb of the basket 44, and may substantiallycorrespond in length to the pre-concentration zone 66 a of thefiltration centrifuge 40. The cone angle in the first basket section 86may be selected based on the specific application and/or other factorsincluding, for example, desired cake thickness or other desired aspectsof the fiber or constituents removed with the water through the sidewall 82.

The side wall 82 of the basket 44 may be configured as a screen so as toseparate or filter the desired material from the liquid medium. Forexample, to separate or filter fiber from the initial slurry or the washwater (depending on the particular zone), the side wall 82 of the basket44 may be configured as a screen adapted to permit the slurry (minus thefiber) and the wash water (and any protein and/or oil washed off thefiber) to pass through the screen while preventing the fiber frompassing therethrough. To this end, the screened side wall 82 may haveseveral configurations. For example, in one embodiment, the side wall 82may be generally solid with a plurality of holes or fenestrations formedtherein and sized so as to achieve the filtration of the desiredmaterial. In another embodiment, the screened side wall 82 may be formedfrom wrapped wedge wire that defines the plurality of openings. In stillfurther embodiments, the screened side wall 82 may be a bar screen, athin metal screen (e.g., mesh screen), or a filter cloth having a metalreinforced design. Those of ordinary skill in the art will recognizeother types of screens that may be used in accordance with embodimentsof the invention. The openings in the screened side wall 82 may varydepending on the specific application and on the type of material beingfiltered. For example, for fiber filtration, it is contemplated that theopenings in side wall 82 may be sized between approximately 35 micronsand approximately 1,500 microns. And in another example, it iscontemplated that the openings in side wall 82 may be sized betweenapproximately 50 microns and approximately 150 microns. These values areexemplary and those of ordinary skill in the art will recognize how todetermine the size of the openings to achieve the filtration of thedesired material.

In one aspect in accordance with various embodiments, the basket 44 isadapted to rotate about a central axis 90 so as to drive the liquidmedium toward the side wall 82 of basket 44. For example, rotation ofthe basket 44 generates a centrifugal force that drives the slurry orfiber/wash water mixture (depending on the stage along the filtrationcentrifuge 40) toward the screened outer side wall 82. This forceessentially presses the slurry or fiber/wash water mixture against thescreen so as to trap the fiber while allowing the liquid medium (and anysmaller constituents such as protein and oil) to pass through thescreen. The first and second hubs 76, 80, which are coupled to thescreened side wall 82, are configured to facilitate rotation of thebasket 44 within the outer housing 42. In this regard, the first hub 76includes an extension portion 92 that extends through an opening 94(FIG. 3) in the first end wall 50 of the outer housing 42, and a flangeportion 96 coupled to side wall 82. As is generally known in the art,first hub 76 may include various seals, bearings, and/or other fittingsthat allow the first hub 76 to rotate relative to the opening 94 in endwall 50 of outer housing 42. As discussed in more detail below, thefirst hub 76 also rotates relative to the conveyor 46 and conduit lines48 that extend within or into the basket 44 (FIG. 3). Those of ordinaryskill in the art will recognize conventional components (e.g., seals,bearings, fittings, etc) that permit such relative movement therebetweenas well.

In a similar manner, second hub 80 includes an extension portion 98 thatextends through an opening 100 (FIG. 3) in the second end wall 52 ofouter housing 42, and a flange portion 102 coupled to side wall 82. Asis generally known in the art, second hub 80 may include various seals,bearings, and/or other fittings that allow the second hub 80 to rotaterelative to the opening 100 in end wall 52 of outer housing 42. Asdiscussed in more detail below, the second hub 80 also rotates relativeto the conveyor 46 that extends within the basket 44 (FIG. 3). Those ofordinary skill in the art will recognize conventional components (seals,bearings, fittings, etc) that permit such relative movementtherebetween. As shown in FIG. 4, the flange portion 102 of second hub80 includes a coupling between the side wall 82 and the second hub 80having a plurality of circumferentially-spaced legs 106 that defineopenings (not shown) therebetween. The openings allow the filteredmaterial exiting the last washing stage, such as washing zone 66 c inFIG. 3 (or enhanced de-watering stage, compaction stage, air dry stage,or other stage adjacent chute 70), to flow to chute 70 and throughoutlet 72, where the material may be collected for further processing.

In reference to FIG. 3, rotation of the basket 44 may be achieved by asuitable motor or other motive force-generating device. By way ofexample, the second hub 80 may be operatively coupled to a motor, shownschematically at 110, so as to cause second hub 80 and thus basket 44 torotate about central axis 90. For example, a suitable belt (not shown)may couple the motor 110 to a pulley 111 on filtration centrifuge 40 torotate basket 44. In one embodiment, the motor 110 may be coupled to acontroller, such as a computer, and shown schematically at 112, forcontrolling the rotational speed of the basket 44. Such a controller 112is generally known to those of ordinary skill in the art. Thus, therotational speed of the basket 44 may be selectively varied depending onthe specific application. In one embodiment, the basket 44 may berotated at a speed (e.g., revolutions per minute) that generates a Gforce between approximately 100 G to 4,000 G (and may depend on basketdiameter, type of material being filtered, etc.) at the side wall 82 ofthe basket 44. In one embodiment, such as for corn dry millingprocesses, the basket 44 may be rotated at a speed so as to generatebetween approximately 300 G and approximately 1,200 G at the side wall82. Those of ordinary skill in the art will recognize that these valuesare exemplary and the speeds may be selected and optimized to meet theneeds of a particular application.

In another aspect of various embodiments, the filtration centrifuge 40,which may include a pre-concentration zone, one or more washing zones,and possible other zones (e.g., de-watering, compaction, air, etc.), mayhave a L/D ratio greater than two. In one embodiment, the filtrationcentrifuge 40 may have a L/D ratio between approximately 2 and 10, andmore preferably between 4 and 6. These values are exemplary and those ofordinary skill in the art will recognize other ratios suitable for aparticular application.

The relatively large L/D ratio may be achieved by using a relativelysmall basket diameter Db (e.g., maximum value such as along secondbasket section 88) and a relatively large basket length Lb. By way ofexample, the basket diameter Db at its maximum value may be betweenapproximately 100 mm and approximately 1,500 mm, and more particularlybetween approximately 200 mm and approximately 1,000 mm. The relativelysmall basket diameter Db of filtration centrifuge 40 provides higher Gforces imposed on the liquid medium (e.g., slurry or fiber/wash watermixture) at the screened side wall 82, and thus allows for a greateramount of liquid to be removed from the filtered material resulting in adryer product. For example, it is anticipated that the fiber materialthat exits the filtration centrifuge 40 via exit chute 70 may be betweenapproximately 55% and approximately 75% water. The relatively largebasket length Lb of filtration centrifuge 40 provides a low cost perfiltration area.

In another aspect of various embodiments, filtration centrifuge 40further includes a conveyor 46 for moving or scrolling the material inthe liquid medium from the first end 74 of the basket 44 toward thesecond end 78 thereof and to keep the filtration area at the screenedside wall 82 clean. As illustrated in FIGS. 3 and 5, in one embodiment,the conveyor 46 may be configured as a generally hollow screw or auger114 generally coaxially disposed within the basket 44. The auger 114includes a first end 116 defined by a first hub 118, a second end 120defined by a second hub 122, and at least one side wall 124 extendingbetween the first and second ends 116, 120 and coupled to the first andsecond hubs 118, 122. The first and second hubs 118, 122 of the auger114 may be operatively coupled to the first and second hubs 76, 80 ofthe basket 44. By way of example, the first and second hubs 76, 80 ofthe basket 44 may include cavities 126, 128 (FIG. 4), respectively, forreceiving the first and second hubs 118, 122 of the auger 114 therein.While the auger 114 may have any suitable shape, in one embodiment, theauger 114 may be generally cylindrical and have a generally circularcross-sectional shape characterized by an auger diameter Da. In oneembodiment, the auger diameter Da may be substantially constant alongthe length of the auger 114. In an alternative embodiment, however, theauger diameter Da may vary along the length of the auger 114, such as byhaving a generally conical shape (not shown). As recognized by those ofordinary skill in the art, other configurations may also be possible.

To facilitate movement of the desired filtered material (e.g., fiber)along the filtration centrifuge 40, the auger 114 may include at leastone generally radially-extending, helical thread 130 projecting from theside wall 124 of the auger 114. The thread 130 includes an outer edge132 configured to be located in close proximity to the inner surface ofthe side wall 82 of the basket 44 (FIG. 3). For example, a small gap (onthe order of 0.3 mm-2.0 mm) may exist between the outer edge 132 of thethread 130 and the side wall 82 of the basket 44 so as to accommodate,for example, relative movement therebetween, yet remain effective forkeeping the filtration area at the screened side wall 82 clean. Asexplained in more detail below, the generally annular space 134 definedbetween the auger 114 and the basket 44 (FIG. 3), and occupied by thethreads 130, provides a fluid flow passage for the liquid medium (e.g.,slurry or wash water) during the filtration of the material (e.g.,fiber). Accordingly, the annular space 134 must be sized to accommodatethe design throughput of the filtration centrifuge 40. In an exemplaryembodiment, for example, the auger 114 may have an auger diameter Dabetween approximately 0.4 Db and 0.8 Db and the distance between theauger 114 and the basket 44 (nearly equal to the height of thread 130)is between approximately 0.01 Db and 0.4 Db. These values are exemplaryand those of ordinary skill in the art may readily determine the augerdiameter Da and/or radial spacing between the auger 114 and the basket44 for specific applications.

In one embodiment, and as illustrated in FIGS. 5 and 6, the auger 114may have a multi-flight configuration (e.g., having multiple helicalthreads extending along at least a portion of the length thereof). Byway of example, the auger 114 may include between 2 and 6 flights, andmore preferably between 3 and 4 flights (4 shown) along at least aportion of the auger length. While each of the flights 130 a, 130 b, 130c, 130 d may extend the full length of the auger 114, in one embodiment,one or more of the flights may extend for less than the full length ofthe auger 114. More particularly, in one exemplary embodiment, themulti-flight configuration of the threads 130 a, 130 b, 130 c, 130 d mayextend along the length of the auger 114 corresponding to the length ofthe pre-concentration zone 66 a and only one of the threads, e.g., 130a, may extend thereafter along the washing zones 66 b, 66 c. In thisregard, it is believed that the multi-flight configuration of thethreads 130 in the pre-concentration zone 66 a at least in parteffectively enhances the filtering of the material from the liquidmedium while preventing the basket 44 from plugging. Those of ordinaryskill in the art will recognize other configurations of threads 130 thatfacilitate the movement of the material through the filtrationcentrifuge 40 to meet the requirements of a particular application, andthe invention is not limited to the particular configuration shown inFIG. 6. For example, auger 114 may have a single flight configuration,such as that shown in FIG. 10.

In addition to the multi-flight configuration of the threads 130 onauger 114, another design variable that allows the auger 114 to beconfigured for specific applications is the pitch P of the threads 130along the length of the auger 114 (FIG. 5). In one embodiment, forexample, the pitch P may vary along the length of the auger 114. Morespecifically, in one exemplary embodiment, the pitch P of the threads130 in the pre-concentration zone 66 a may be relatively large, such asbetween 0.1 Db and 0.6 Db, and decrease in the washing zones 66 b, 66 c.For example, the pitch in the washing zones 66 b, 66 c may be between0.1 Db and 0.4 Db. In this regard, it is believed that the relativelylarge pitch configuration of the threads 130 in the pre-concentrationzone 66 a at least in part effectively enhances the filtering of thematerial from the liquid medium while preventing the basket 44 fromplugging. Those of ordinary skill in the art will recognize othervariable pitch configurations of threads 130 that facilitate themovement of the material through the filtration centrifuge 40 to meetthe requirements of a particular application, and the invention is notlimited to the particular pitch configuration shown in FIGS. 5 and 6.For example, the pitch P may be relatively constant along the length ofthe auger 114.

In a further aspect in accordance with various embodiments, the auger114 is adapted to rotate about central axis 90. Rotation of the auger114 causes the thread(s) 130 to rotate in order to move the filteredmaterial (e.g., fiber) down the filtration centrifuge 40. The first andsecond hubs 118, 122, which are coupled to the side wall 124 of auger114, are configured to facilitate rotation of the auger 114 within thebasket 44. In this regard, the first hub 118 includes an extensionportion 136 that extends into the cavity 126 of the first hub 76 of thebasket 44, and a flange portion 138 coupled to the side wall 124. As isgenerally known in the art, first hub 118 may include various seals,bearings, and/or other fittings that allow the first hub 118 to rotaterelative to the first hub 76 of the basket 44. The first hub 118 ofauger 114 also rotates relative to the conduit lines 48 that extendwithin the interior of the auger 114. Those of ordinary skill in the artwill recognize conventional components (e.g., seals, bearings, fittings,etc.) that permit such relative movement therebetween as well.

In a similar manner, second hub 122 includes an extension portion 140that extends into the cavity 128 of the second hub 80 of the basket 44,and a flange portion 142 coupled to the side wall 124. As is generallyknown in the art, second hub 122 may include various seals, bearings,and/or other fittings that allow the second hub 122 to rotate relativeto the second hub 80 of the basket 44. As there may be no conduit lineextending through second hub 122, the hub may have a closedconfiguration (FIG. 5).

Rotation of the auger 114 may be achieved by a suitable motor or othermotive force-generating device. For example, one of the first or secondhubs 118, 122 may be operatively coupled to an electric motor so as tocause the auger 114 to rotate about central axis 90 (not shown).Although the motor that rotates the auger 114 may be separate from themotor 110 that rotates the basket 44, in one exemplary embodiment, andas schematically illustrated in FIG. 3, motor 110 may also be used torotate the auger 114. Those of ordinary skill in the art will recognizethat if separate motors are used to rotate the basket 44 and auger 114,the motors may be controlled by the same controller, such as controller112, or by separate controllers (not shown).

In the embodiment illustrated in FIG. 3, the same motor 110 andcontroller 112 provide for and control the speed of both the basket 44and the auger 114. Although the filtration centrifuge 40 may beconfigured such that the basket 44 and auger 114 rotate at the samespeed, in an exemplary embodiment, the basket 44 and auger 114 may beconfigured to rotate at different speeds. In this regard, the filtrationcentrifuge 40 may include a gear box, schematically shown at 144, toprovide for the different rotational speeds between the basket 44 andthe auger 114. Such gear boxes 144 and their internal components aregenerally known in the art and a detailed description herein will beomitted. In one embodiment, for example, the gear box 144 may beconfigured to reduce the rotational speed of the auger 114 relative tothe basket 44. Alternatively, the gear box 144 may be configured toincrease the rotational speed of the auger 114 relative to the basket44.

The gear box 144 may be operatively coupled to the controller 112 forcontrolling the differential in the rotational speeds (schematicallyshown in FIG. 3). For example, the gear box 144 may be coupled to asmall motor (not shown), which is operatively coupled to the controller112, that controls the differential rotational speed between the basket44 and the auger 114. In one embodiment, the gear box 144 may beconfigured such that a differential in rotational speed between thebasket 44 and auger 114 is between 0 and about 200 rpm. This range isexemplary and, depending on the configuration of the gear box 144, thoseof ordinary skill in the art will recognize that the range may beadjusted to meet a specific application. Those of ordinary skill in theart may also recognize other known devices for creating a differentialspeed between the basket 44 and auger 114, including, for example,various gear reduction designs and hydraulic drives.

The filtration centrifuge 40 includes a plurality of generallyconcentric conduit lines 48 generally coaxially disposed in auger 114for supplying liquid medium (e.g., the slurry and wash water) to thecentrifuge 40. The number of conduit lines 48 generally corresponds tothe number of zones 66 in the filtration centrifuge 40. By way ofexample, and as shown in FIGS. 3 and 5, the filtration centrifuge 40includes one pre-concentration zone 66 a and two washing zones 66 b, 66c. Accordingly, fluid conduit lines 48 include one slurry supply line 48a and two wash water supply lines 48 b, 48 c. The slurry supply line 48a includes an inlet 146 for receiving the whole stillage byproduct andan outlet 148 positioned in the pre-concentration zone 66 a of thefiltration centrifuge 40 and within the interior of auger 114. In asimilar manner, the first water supply line 48 b includes an inlet 150(FIGS. 1 and 6) for receiving wash water and an outlet 152 positioned inthe first washing zone 66 b and within the interior of the auger 114.The second water supply line 48 c includes an inlet 154 (FIGS. 1 and 6)for receiving wash water and an outlet 156 positioned in the secondwashing zone 66 c and within the interior of the auger 114.

Operation of the filtration centrifuge 40 will now be described. Tofacilitate understanding of various aspects of the invention, operationof the filtration centrifuge 40 will be described in the context offiber filtration in a corn dry mill process. It should be appreciated,however, that the filtration centrifuge 40 may be used in a wider rangeof applications and is not limited in use to the corn dry mill processdescribed herein. The motor 110 is activated so as to initiate rotationof the basket 44 and the auger 114 at their designated speeds, asdescribed above. As best illustrated in FIG. 7, the whole stillagebyproduct, or slurry, is supplied to the inlet 146 of the slurry conduit48 a so as to flow through the outlet 148 and into a chamber 158 withinthe auger 114 and generally associated with the pre-concentration zone66 a. The chamber 158 includes a generally cone-shaped guide 160 thatdirects the slurry into the annular space 134 between the auger 114 andthe basket 44. In this regard, the auger 114 may include at least oneopening 162 (two shown) that provides fluid communication between thechamber 158 and the annular space 134. Due to the rotation of the auger114 and the resulting motion of the threads 130, the slurry is movedalong the length of the pre-concentration zone 66 a and fiber isfiltered from the slurry by allowing the water, protein, oil, and otherrelatively small constituents of the slurry to pass through the screenedside wall 82 of the basket 44 and drain into hopper 60 a while the fiberand possibly relatively large constituents of the slurry are retained inthe basket 44.

Due to the relative rotation between the conduit lines 48 and the auger114, it may be possible for fiber to pass by the cone guide 160 withinthe auger 114 and pass into the washing zones 66 b, 66 c. To prevent orreduce the likelihood of such an event, the filtration centrifuge 40 mayinclude a leak chamber 164 positioned about an end of the guide 160. Thechamber 164 is defined by a baffle plate 168 at one end thereof and by aclosed web 170 at an opposite end thereof and extending between theguide 160 and the auger 114. The auger 114 may include at least oneopening 172 (two shown) that provides fluid communication between theleak chamber 164 and the annular space 134. Thus, should any fiber leakpast the end of the guide 160 and into leak chamber 164, the fiber willflow through the openings 172 and into the annular space 134. In thisway, the likelihood of fiber passing beyond the baffle plate 168 issignificantly reduced. As explained in more detail below, fiber isundesirable in the washing zones 66 b, 66 c due to possible plugging ofnozzles used in those zones.

At the end of the pre-concentration zone 66 a, the fiber has beensufficiently concentrated so as to allow the fiber to be washed. Forexample, in one embodiment, the fiber is believed to be between about55% and about 75% water at the end of the pre-concentration zone 66 a.At such concentration levels, the fiber may be effectively washed toremove the additional protein, for example, that remains associated withthe fiber after the initial pre-concentration zone 66 a (e.g., utilizingdisplacement washing techniques). To this end, the threads 130 of theauger 114 move the fiber along the length of the filtration centrifuge40 and into the first washing zone 66 b (FIG. 1). In reference to FIGS.3, 7 and 8, wash water is supplied to the inlet 150 of the first waterconduit 48 b so as to flow through the outlet 152 and into a chamber 174generally associated with the first washing zone 66 b. The chamber 174is bounded on one side by the baffle plate 168 and bounded on theopposite side by a conical member 176, which includes an end adjacentthe conduit lines 48. The chamber 174 may further include a supportmember 180 that supports the water conduit lines 48 b, 48 c withinchamber 174.

The first washing zone 66 b includes at least one rinsing stage 181 aand at least one de-watering stage 181 b. For example, as illustrated inFIG. 8, the first washing zone 66 b includes two rinsing/de-wateringcycles. This is exemplary and those of ordinary skill in the art willrecognize that the number of rinsing/de-watering cycles may varydepending on the specific application. In the rinsing stage 181 a, washwater is added to the fiber to remove the additional protein, oil, etc.associated with the fiber. The de-watering stage 181 b separates thefiber by removing the wash water, and any protein washed from the fiber.

In this regard, in the rinsing stage 181 a, wash water flows intochamber 174 from conduit line 48 b and then is injected into the annularspace 134 via at least one, and preferably a plurality of, nozzles 182.In one embodiment, for example, the nozzles 182 may be circumferentiallyspaced about the auger 114 at a fixed axial location (e.g., in a ringconfiguration). The nozzles 182 may be susceptible to plugging by fiberand it is for at least this reason that it is undesirable to have fiberpresent in chamber 174. The wash water injected into the annular space134 in the washing zone 66 b effectively washes the fiber. Additionally,the fiber is filtered from the wash water by moving the fiber/wash watermixture through the de-watering stage 181 b. This allows the wash waterand any additional protein, oil, etc. to pass through the screened sidewall 82 of the basket 44 and drain into hopper 60 b while the fiber isretained in the basket 44. As noted above, the fiber is subjected to asecond rinsing/de-watering cycle 181 a, 181 b in the first washing zone66 b. At the end of the first washing zone 66 b, the fiber has beenwashed and filtered (e.g., twice) such that it may have approximatelythe same concentration of water as at the end of the pre-concentrationzone 66 a (e.g., between about 55% and about 75% water). Depending onthe amount of water added in the first washing zone 66 b and theparticular configuration of the filtration centrifuge 40, it may bepossible to further reduce the water concentration of the fiber whilestill providing effective washing.

After the first washing zone 66 b, the threads 130 of the auger 114continue to move the fiber along the length of the filtration centrifuge40 and into the second washing zone 66 c having rinsing/de-wateringstages 189 a, 189 b. In reference to FIGS. 3 and 7-9, wash water issupplied to the inlet 154 of the second water conduit 48 c so as to flowthrough the outlet 156 and into a chamber 184 generally associated withthe second washing zone 66 c. The chamber 184 is bounded on one side bythe conical member 176 and bounded on the opposite side by plate 186.Wash water flows into chamber 184 from conduit line 48 c and then isinjected into the annular space 134 via at least one, and preferably aplurality of, nozzles 188, which may be similar to nozzles 182. The washwater injected into the annular space 134 in the washing zone 66 ceffectively washes the fiber. Additionally, the fiber is filtered fromthe wash water by moving the fiber/wash water mixture through thede-watering stage 189 b. This allows the wash water and any additionalprotein, oil, etc. to pass through the screened side wall 82 of thebasket 44 and drain into hopper 60 c while the fiber is retained in thebasket 44. As noted above, the fiber is subjected to a secondrinsing/de-watering cycle 189 a, 189 b in the second washing zone 66 c.At the end of the second washing zone 66 c, the fiber has been washedand filtered such that it may have approximately the same concentrationof water as at the end of the pre-concentration zone 66 a. As notedabove, however, it may be possible to reduce the water concentration inthe second washing zone 66 c.

The washed and filtered fiber exits adjacent the second end 78 of thebasket 44 and flows into the exit chute 70 and to outlet 72. When thefiber exits the chute 70, the fiber can be further processed asdiscussed further below to result in a desired product, such as DWGS orDDGS. In one example, the fiber can be transported to a remote site forfurther processing. Moreover, the slurry, which includes water, protein,oil, etc. that passes through the screened side wall 82 in thepre-concentration zone 66 a, as well as the wash water, protein, oil,etc. that passes through the screened side wall 82 in the washing zones66 b, 66 c are collected to define the thin stillage then transportedand further processed as described below. Optionally, a portion of theslurry and/or wash water collected in washing zones 66 a, 66 b, and/or66 c may be piped back to the optional paddle screen 34 for furtherreprocessing.

In one aspect in accordance with various embodiments, the wash water forthe washing zones 66 b, 66 c may implement counter current washingmethodologies. For example, clean wash water may be supplied to the lastwashing zone 66 c via the inlet 154 of second water conduit 48 c. Thewash water that is collected by hopper 60 c, which may include water,protein, oil, etc., is then directed through outlet 62 c and supplied tothe inlet 150 of the first water conduit 48 b. This once used wash wateris then used to wash the fiber in the first washing zone 66 a. The washwater that is collected by hopper 60 b may then be combined with theslurry (minus the collected fiber) collected in hopper 60 a and passedto the next step in the corn dry mill process as the thin stillage.Those of ordinary skill in the art will recognize how to implement thecounter current washing methodology when there are additional washingzones or other zones in the filtration centrifuge 40.

In a further aspect in accordance with various embodiments, filtrationcentrifuge 40 may be configured to include an air blowing zone. Such anair blowing zone is adapted to further dry the fiber (e.g., reduce thewater concentration of the fiber) by blowing hot air (or other suitablefluid) over the fiber. In this regard, a hot air source may be in fluidcommunication with the annular space 134 adjacent the second end 78 ofthe basket 44, such as with appropriate conduits. The hot air may besupplied to the filtration centrifuge 40 via its second end, forexample. The hot air may be introduced into the fiber during, forexample, the de-watering stage of the last washing zone 66 c.Alternatively, a separate stage may be added to filtration centrifuge 40for the purpose of drying the fiber using hot air or other suitablefluids.

In another aspect in accordance with various embodiments, filtrationcentrifuge 40 may include an adjustable brush assembly adapted toimprove the filtration rate and re-generate the filtration surface alongthe screened side wall 82 of the basket 44. In this regard, the auger114, and more particularly, the outer edge 132 of the threads 130 mayinclude a brush (not shown) for sweeping across the screened side wall82 of the basket 44. The brush may be used, for example, when thematerial being filtered has a size on the order of the gap between theouter edge 132 of the threads 130 and the inner surface of the side wall82 of the basket 44. In such applications, the brush may extend acrossthe gap so as to loosen the material from the screened side wall 82 andthus prevent or reduce plugging, as well as to facilitate movement ofthe material along the centrifuge.

The features of the filtration centrifuge 40, including, for example,the multi-flight design of the threads 130 of the auger 114, the conicalshape of the basket 44 in the pre-concentration zone 66 a, therelatively large L/D ratio at which the centrifuge is capable ofoperating, and/or other features allows the filtration centrifuge 40 tohave a compact design. In this regard, one or more of the featuresallows the filtration centrifuge 40 to be a single, self-containeddevice that performs both the initial filtering of the liquid medium toremove the desired filtered material, and washing of the material toremove additional constituents, such as additional protein, oil, etc.therefrom.

The ability of filtration centrifuge 40 to more effectively “dry” (i.e.,reduce the concentration of water in the filtered material) in thepre-concentration zone 66 a, in turn, allows the use of suchdisplacement washing techniques. If the concentration of water in thefiltered material is too high (as in conventional systems) displacementwashing techniques may not prove beneficial and as a result,less-effective dilution washing techniques are implemented. In additionto the above, the filtration centrifuge 40 may be made more compactlyand therefore utilize floor space within a manufacturing facility in amore efficient manner than present systems. Moreover, such a design mayalso reduce the capital costs of the device, the labor and associatedcosts for maintaining the device, and the operating costs (e.g., useless water, etc.).

Furthermore, one or more of the features of filtration centrifuge 40allows the filtered material to exit the centrifuge in a “dryer”condition as compared to existing filtration systems. Heretofore, suchfiltering has been typically achieved by a decanter centrifuge. Forexample, filtration centrifuge 40 may provide the filtered material at awater concentration of between about 55% and about 75% water, which is asignificant reduction compared to conventional filtration systems.Providing a dryer product may result in additional benefits.Additionally, energy costs associated with operation of a dryer is alsoexpensive. Significant energy savings may be achieved by having just arelatively small change in the concentration of water in the material.Alternatively, depending on the application, the dryer step may beomitted in the post processing of the fiber. Thus, the ability offiltration centrifuge 40 to provide a dryer material may allowmanufacturers to forego or reduce the costs associated with these postprocessing steps.

In addition, one or more of the features results in the filtrationcentrifuge 40 being flexible and robust in use. For example, it isbelieved that filtration centrifuge 40 is capable of effectivelyfunctioning over a wide range of operating parameters. For example,filtration centrifuge 40 is capable of effectively accommodating a broadrange of materials for filtering (e.g., fiber), a broad range ofmaterial sizes, as well as material that may be sharp or otherwisedifficult to handle. In addition, the filtration centrifuge 40 iscapable of accommodating an input slurry or feed having a wideconcentration range (i.e., the filtration centrifuge 40 is generally notsensitive to the concentration of the input material).

Another embodiment of a filtration centrifuge is shown in FIG. 10.Filtration centrifuge 200 is structurally and operationally similar tofiltration centrifuge 40 shown and described above. Accordingly, adetailed description of the filtration centrifuge 200 is not deemednecessary. Instead, a detailed description of the modifications betweenthe filtration centrifuges 40, 200 will be provided. Similar referencenumbers in FIG. 10 will refer to like features shown in FIGS. 3-9.Filtration centrifuge 200 includes an outer housing 202, an innerhousing or basket 204, a conveyor 206 generally coaxially disposed inthe basket 204, and a plurality of conduit lines 208 generally coaxiallydisposed in conveyor 206. The plurality of conduit lines 208 include oneslurry supply line 208 a and two wash water supply lines 208 b, 208 c.The conveyor 206 may be configured as an auger 210 similar to thatdescribed above.

One modification is directed to the number and/or types of zonesprovided in filtration centrifuge 200. For example, and as explained inmore detail below, filtration centrifuge 200 may include apre-concentration zone 212 a, a washing zone 212 b, a de-watering zone212 c, and a compaction zone 212 d. The pre-concentration zone 212 a issimilar to that described above in terms of the configuration andoperation of the conduit lines 208, auger 210, basket 204, and housing202 along with the pre-concentration zone 212 a, which includescorresponding funnel-shaped hopper 222 a and outlet 224 a, and thus, afurther description will not be provided herein. The washing zone 212 b,however, has been modified. In regard to filtration centrifuge 40, eachof the washing stages 66 b, 66 c included two rinsing/de-watering cyclesspaced axially along the central axis 90 of filtration centrifuge. Asshown in FIG. 10, after the pre-concentration zone 212 a, there is onlyone washing zone 212 b. Moreover, instead of one or morerinsing/de-watering cycles axially spaced along the centrifuge, auger210 includes a plurality of nozzles 214 generally uniformly axially andcircumferentially spaced along washing zone 212 b. Such an arrangementprovides a relatively uniform injection of wash water into washing zone212 b. In essence, the washing zone 212 b becomes a rinse cycle withouta corresponding de-watering cycle. Those of ordinary skill in the artshould recognize that fluid (e.g., water, protein, oil, etc) will beejected from the basket 204 due to the centrifugal forces acting on thematerial. However, this occurs at locations where a relatively largeamount of wash water is being introduced (by nozzles 214). In contrast,de-watering occurs when no wash water or alternatively, a relative smallamount of fluid is being introduced.

One modification is directed to the number and/or types of zonesprovided in filtration centrifuge 200. For example, and as explained inmore detail below, filtration centrifuge 200 may include apre-concentration zone 212 a, a washing zone 212 b, a de-watering zone212 c, and a compaction zone 212 d. The pre-concentration zone 212 a issimilar to that described above in terms of the configuration andoperation of the conduit lines 208, auger 210, basket 204, and housing202 along the pre-concentration zone 212 a and thus, a furtherdescription will not be provided herein. The washing zone 212 b,however, has been modified. In regard to filtration centrifuge 40, eachof the washing stages 66 b, 66 c included two rinsing/de-watering cyclesspaced axially along the central axis 90 of filtration centrifuge. Asshown in FIG. 10, after the pre-concentration zone 212 a, there is onlyone washing zone 212 b. Moreover, instead of one or morerinsing/de-watering cycles axially spaced along the centrifuge, auger210 includes a plurality of nozzles 214 generally uniformly axially andcircumferentially spaced along washing zone 212 b. Such an arrangementprovides a relatively uniform injection of wash water into washing zone212 b. In essence, the washing zone 212 b becomes a rinse cycle withouta corresponding de-watering cycle. Those of ordinary skill in the artshould recognize that fluid (e.g., water, protein, oil, etc) will beejected from the basket 204 due to the centrifugal forces acting on thematerial. However, this occurs at locations where a relatively largeamount of wash water is being introduced (by nozzles 214). In contrast,de-watering occurs when no wash water or alternatively, a relative smallamount of fluid is being introduced.

In operation, wash water is supplied to the first water conduit 208 b soas to flow through its outlet and into a chamber 216 in auger 210generally associated with the washing zone 212 b. The chamber 216 isbounded on one side by baffle plate 168 and bounded on the opposite sideby a conical member 218. The conical member 218 includes a gapped orwebbed support member 220 that allows wash water to flow thereby. Thewash water in chamber 216 is injected into the annular space 134 via thenozzles 214 to wash the fiber and remove any remaining protein, oil,etc. that may be associated with the fiber after the initialpre-concentration zone 212 a. In the washing zone 212 b, wash waterhaving a first concentration of constituents (e.g., protein) is injectedand water having a second concentration of constituents, which is higherthan the first concentration, is ejected from the side wall 82 of basket204. This fluid drains into one or more hoppers 222 b, 222 c and throughrespective outlets 224 b, 224 c. While two hoppers 222 b, 222 c may beassociated with washing zone 212 b, those of ordinary skill in the artwill recognize that only one hopper may be provided for the washing zone212 b. When washing zones get relatively long, there may be someadvantages with having multiple hoppers within a single washing zone.For example, the counter-current washing technique may be more effectiveusing multiple hoppers. The invention should not be limited to havingone hopper per zone, but those of ordinary skill will recognize that thenumber of hoppers (and/or compartments defined by interior panels 64)may vary depending on the particular application.

After the washing zone 212 b, the threads 130 of auger 210 move thefiber along the filtration centrifuge 200 and into a de-watering zone212 c. The de-watering zone 212 c is configured to remove the wash waterand any additional protein, oil, etc. from the fiber, but with little tono addition of more wash water (e.g., there is no wash water injectedinto the annular space 134 along the de-watering zone 212 c viainjection nozzles). Along the de-watering zone 212 c, the water,protein, oil, etc. that pass through the screened side wall 82 of basket204 drains into hopper 222 d with the fiber being retained in the basket204. Thus, the concentration of water in the filtered material may bereduced in the de-watering zone 212 c.

Another modification in this embodiment is the inclusion of a compactionzone 212 d in filtration apparatus 200. In this regard, the basketdiameter Db may vary along the length of the basket 204 adjacent thesecond end thereof. By way of example, basket 204 may include a thirdbasket section 226 adjacent the second end 78 of the basket. The thirdbasket section 226 may include a generally inwardly tapered (i.e.,converging) or cone-shaped configuration in a direction from first end74 toward second end 78. In one embodiment, the third basket section 226may extend for about 10% to about 30% of the length of the basket 204,and may substantially correspond in length to the compaction zone 212 dof the filtration centrifuge 200. It is believed that the conical shapeof the basket 204 along this portion essentially compacts the filteredmaterial (e.g., fiber) due to a reduced cross-sectional area (andtherefore volume) along this region. The water, protein, oil, etc. thatpass through the screened side wall 82 of basket 204 in the compactionzone 212 d drains into hopper 222 d and through outlet 224 d. Thiscompaction further reduces the concentration of water in the filteredmaterial resulting in dryer fiber being output from the filtrationcentrifuge 200. The cone angle in the third basket section 226 may beselected based on the specific application and/or other factorsincluding, for example, desired cake thickness or other desired aspectsof the fiber or constituents removed with the water through the sidewall 82.

In one embodiment, an additional pathway for water to escape as a resultof the squeezing of the filtered material may be provided in thecompaction zone 212 d. In this regard, the auger 210 may have side wall124 configured as a screen 228 for at least a portion of the length ofthe compaction zone 212 d. In this way, it is possible for fluid toescape not only through the screened side wall 82 of basket 204, butalso through the side wall 124 of the auger 210 along at least a portionof this zone. As discussed in more detail below, the fluid which passesthrough the screen 228 may be directed into the annular space 134 in thede-watering zone 212 c. Alternatively, the fluid may be removed fromauger 210 through other means such as a drain conduit through the secondend of filtration centrifuge 200.

In still a further embodiment, and referring back to FIG. 1, to releasestarch, germ (oil), protein, fiber and other constituents from corn, thecorn goes through a grinding process. Such grinding process(es) canresult in some amount of a specific constituent being ground torelatively fine particles (e.g., less than about 50 microns). Forexample, relatively small pieces of fiber, referred to in the industryas fine fiber, are typically produced therefrom. Thus, while arelatively high percentage of the fiber does not get ground into verysmall particles, some relatively small percentage of the fiber may beground into small particles. Sufficiently small constituent particlesmay still reside in the whole stillage byproduct. Fiber having a sizeless than that of the screen of the filtration centrifuge 40 may passthrough and to subsequent steps of the corn dry mill process. In thisregard and in accordance with an aspect of the invention, the fibercollected in basket 204 may in essence be used as a filtering medium forfine fiber. More particularly, the fiber in basket 204 near the secondend 78 thereof is relatively thick (e.g., between about 55% and about75% water) and thus effectively comprises a relatively tight network offibers that, in essence, collectively forms a matted material. Thismatted network of fibers collected in basket 204 may be used as a“filter” to separate the fine fiber from a liquid medium. To this end,it is believed that the network of fibers may include voids or openingsthat are smaller than the fine fiber thereby trapping the fine fiberwithin the network of fibers already collected in basket 204.

To configure filtration centrifuge 200 for such a purpose, the slurrycarrying the fine fiber (e.g., the output from pre-concentration zone212 a) may be supplied to the second water conduit 208 c, the exit ofwhich is within a chamber 230 generally associated with the de-wateringzone 212 c. The chamber 230 is bounded on one side by the conical member218 and bounded on the opposite side by plate 232. The auger 210includes one or more apertures 234 that provide fluid communicationbetween chamber 230 and the annular space 134. The slurry with the finefiber flows into chamber 230 from conduit line 208 c and then flows intoannular space 134 via the apertures 234. Due to the forces imposed byrotation of the basket 204 and/or auger 210, the liquid medium whichcarries the fine fiber flows through the matted fibers already collectedin basket 204, flows through the side wall 82 of basket 204, and drainsinto the hopper 222 d. It is believed that the fluid collected in hopper222 d has a significantly reduced amount of fine fiber therein.Moreover, the fine fiber may be filtered from the liquid medium usingthe same apparatus that performs the initial filtration for the largepieces and washing of the fiber. This significantly reduces the costs,maintenance, etc. that is associated with conventional apparatus forfiltering fine fiber. With the fine fiber removed from the liquidmedium, the thin stillage may be transported for further processing inthe corn dry mill process.

Additional advantages and modifications will readily appear to thoseskilled in the art. For example, while the filtration centrifuges 40,200 have been described herein as being in a generally horizontalorientation, other orientations are possible, including the centrifugeshaving a generally vertical orientation. Additionally, the centrifuges40, 200 may be an open type of system or configured for closedoperation. The filtration centrifuges 40, 200 may also be designed forpressurized operation. Still further, the filtration centrifuges 40, 200may be operated continuously or configured to work in a batch mode ofoperation. As illustrated in FIGS. 3 and 10, the filtration centrifuges40, 200 may include a basket cleaning system 192, including a pluralityof nozzles 194 situated, for example, along the upper wall 54 a of theouter housing 42, 202, respectively. The basket cleaning system 192provides backwashing for cleaning the baskets 44, 204. Furthermore,those of ordinary skill in the art should recognize that the number andtypes of zones may be selected based on the specific application. Forexample, a filtration centrifuge in accordance with an embodiment mayinclude a pre-concentration zone without any washing zones. Such anembodiment may further include a de-watering zone, and/or a compactionzone, and/or an air blowing zone. Thus, the number and types of zonesmay be selected based on a specific application.

With further reference again to FIG. 2, although a single filtrationcentrifuge 40 is depicted, it should be understood that a plurality offiltration centrifuges 40 may be situated in-line and utilized forseparating the whole stillage byproduct into its insoluble solidsportion (fiber) and thin stillage portion. And in an alternateembodiment, it is contemplated that the filtration centrifuge 40 can bereplaced by a standard pressure screen, decanter centrifuge, a paddlescreen, or other like devices as are known in the art to separate thewhole stillage byproduct into the insoluble solids portion and thinstillage portion then further processed as discussed below. One suchsuitable pressure screen is the PS-Triple available from Fluid-Quip,Inc. of Springfield, Ohio. One such suitable decanter centrifuge is theNX-944HS available from Alfa Laval of Lund, Sweden. And one suchsuitable paddle screen is the FQ-PS32 available from Fluid-Quip, Inc. ofSpringfield, Ohio.

As further shown in FIG. 2, the thin stillage underflow from thefiltration centrifuge 40 is piped to join up with the underflow from theoptional paddle screen 34. After which time, the thin stillage portionmay be optionally subjected to a standard pressure screen 250, as isknown in the art, to further aid in separation of any fine fiber fromthe thin stillage portion. As indicated above, fiber having a size lessthan that of the screen of the filtration centrifuge 40 and/or optionalpaddle screen 34 may pass through and to subsequent steps of the corndry mill process. At the pressure screen 250, the separated fine fibercan be separated from the thin stillage and piped back to the filtrationcentrifuge 40 whereat the fine fiber may be filtered out. In oneexample, the matted network of fibers collected in basket 204 (FIG. 10)may be used as a “filter” to separate the fine fiber from a liquidmedium, and further processed as discussed below. One such suitablepressure screen 250 is the PS-Triple available from Fluid-Quip, Inc. ofSpringfield, Ohio. In an alternate embodiment, the optional pressurescreen 250 may be replaced with a standard paddle screen or decantercentrifuge, as are mentioned above, or other like device, to aid inseparation of the fine fiber from the thin stillage portion.

After the optional pressure screen 250, the underflow or remaining thinstillage portion is then piped and subjected to a nozzle centrifuge 252,as is known in the art. The nozzle centrifuge 252 can be provided withwashing capabilities so that fresh water, along with the thin stillageportion, can be supplied to the nozzle centrifuge 252. The additionalfresh water allows for easier separation of the thin stillage into itsprotein portion and water soluble solids portion. The heavier proteinportion separates from the water soluble solids portion and is removedas the underflow whereas the lighter water soluble solids portion, whichincludes oil, can be removed as the overflow. One such suitable nozzlecentrifuge 252 is the FQC-950 available from Fluid-Quip, Inc. ofSpringfield, Ohio. In an alternate embodiment, the nozzle centrifuge 252can be replaced with a standard cyclone apparatus or other like device,as are known in the art, to separate the thin stillage portion into theunderflow protein portion and overflow water soluble solids portion. Onesuch suitable cyclone apparatus is the RM-12-688 available fromFluid-Quip, Inc. of Springfield, Ohio.

The underflow protein portion from the nozzle centrifuge 252 is furtherpiped and subjected to decanter centrifuge 254 to dewater the proteinportion. The decanter centrifuge 254 is standard and known in the art.One such suitable decanter centrifuge 254 is the NX-944HS available fromAlfa Laval of Lund, Sweden. Other like devices are contemplated. Theseparated water portion or filtrate from the decanter centrifuge 254 maybe recycled back, for example, to the liquefaction step 16 or thefermentation step 20 for reuse in the dry mill process. The dewateredprotein portion is then dried, such as by being sent to a dryer 256, asis known in the art. In an alternate embodiment, the dewatered proteinportion can be subjected to vacuum filtration or other drying methods,as are known in the art. The final dried protein product defines a highprotein corn meal that includes at least 40 wt % protein on a dry basisand which may be sold as pig or chicken feed, for example. In anotherembodiment, the high protein corn meal includes at least 45 wt % proteinon a dry basis. In another embodiment, the high protein corn mealincludes at least 50 wt % protein on a dry basis. In yet anotherembodiment, the high protein corn meal includes at least 60 wt % proteinon a dry basis. In still another embodiment, the high protein corn mealincludes about 56 wt % protein on a dry basis. The resulting highprotein corn meal may be sold at a much higher cost per ton than DDGS orDWGS.

With continuing reference to FIG. 2, the overflow water soluble solidsportion, which includes oil as well as minerals and soluble proteins, ispiped from the nozzle centrifuge 252 and subjected to a set of threeevaporators 260 a, 260 b, and 260 c, as are known in the art, to beginseparating the soluble solids from the water soluble solids portion. Theevaporators 260 a-c evaporate the liquid portion of the water solublesolids portion. Thereafter, the water soluble solids portion can bepiped and subjected to an optional oil recovery centrifuge 261, as isknown in the art, so that oil can be removed therefrom. One suchsuitable oil recovery centrifuge 261 is the ORPX 617 available from AlfaLaval of Lund, Sweden. In one example, the final recovered oil productcan include between about 40 wt % to about 60 wt % of the total corn oilin the corn. In comparison to typical oil recovery in a standard drymill process, oil recovery centrifuge 261 can function at a highercapacity because the water soluble solids portion, which is subjected tothe oil recovery centrifuge 261, includes less liquid and less proteinthan normal.

The remainder of the water soluble solids portion can be piped andsubjected to another set of three evaporators 260 d, 260 e, and 260 fwhereat the liquid portion is further evaporated from the water solublesolids portion to ultimately yield a soluble solids portion. While thewater soluble solids portion is subjected to two sets of threeevaporators 260 a-c, 260 d-f, it should be understood that the number ofevaporators and sets thereof can be varied, i.e., can be more or less,from that shown depending on the particular application and resultdesired.

The resulting soluble solids portion may be combined with the insolublesolids portion, e.g., fiber, received from the filtration centrifuge 40to provide distillers wet grains with soluble (DWGS), which may befurther dried by a drier 262, as is known in the art, to providedistillers dry grains with solubles (DDGS), both of which can be sold todairy and beef feedlots. In another example, the soluble solids portionmay be used as a natural fertilizer.

Accordingly, in this dry mill process, neither the DDGS nor DWGS receivethe typical concentrated syrup from the evaporators 260. While thischange from the typical dry mill process 10 results in a lower crudeprotein content in the DDGS and DWGS, this decrease is insubstantial,particularly, when the economic advantages of producing the high proteincorn meal are realized. And, despite the lower protein content, the DDGSand DWGS may still be sold to beef and dairy feedlots as cattle feed.

While the present invention has been illustrated by a description ofvarious embodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Thus, the invention in its broader aspects istherefore not limited to the specific details, representative apparatusand method, and illustrative example shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of applicant's general inventive concept.

What is claimed is:
 1. A system for producing grain meal from a wholestillage byproduct, the system comprising: a first apparatus thatreceives a whole stillage byproduct, wherein the first apparatusseparates the whole stillage byproduct into an insoluble solids portionand a thin stillage portion, which includes protein; a second apparatusthat is situated after the first apparatus and prior to any evaporatorand that receives the thin stillage from the first apparatus, whereinthe second apparatus separates the thin stillage portion into only asolids portion, including the protein, and a water soluble solidsportion; an evaporator that is situated after the second apparatus andthat receives the water soluble solids portion but does not receive theseparated solids portion, wherein the evaporator separates solublesolids from the water soluble solids portion, via evaporation; and adryer that is situated after the second apparatus and that dries theseparated solids portion, including the protein, to define a grain mealthat includes at least 40 wt % protein on a dry basis.
 2. The system ofclaim 1 wherein the first apparatus is situated after a distillationcolumn and receives the whole stillage byproduct produced via a graindry-milling process.
 3. The system of claim 1 wherein the secondapparatus separates the thin stillage portion, via weights, into thesolids portion, including the protein, and the water soluble solidsportion.
 4. The system of claim 1 wherein the first apparatus isselected from a filtration centrifuge, a decanter centrifuge, a pressurescreen, or a paddle screen and the second apparatus is selected from anozzle centrifuge or a cyclone apparatus.
 5. The system of claim 1further comprising a second dryer that receives and dries the separatedinsoluble solids portion, which includes fiber.
 6. The system of claim 1for producing a corn meal from the whole stillage byproduct and whereinthe separated protein portion defines a corn meal that includes at least40 wt % protein on a dry basis.
 7. The system of claim 1 furthercomprising a dewatering device that is situated prior to the dryer andreceives the solids portion, including the protein, from the secondapparatus, wherein the dewatering device dewaters the solids portion,including the protein, and wherein the dryer dries the dewatered solidsportion, including the protein, to define the grain meal that includesat least 40 wt % protein on a dry basis.
 8. The system of claim 1further comprising a third apparatus that is situated after the firstapparatus and that receives the insoluble solids portion and whereat anadditional thin stillage portion is separated from the insoluble solidsportion.
 9. A method for producing a grain meal from a whole stillagebyproduct comprising: separating the whole stillage byproduct into aninsoluble solids portion and a thin stillage portion, which includesprotein; prior to any evaporation step, separating the thin stillageportion into only a solids portion, including the protein, and a watersoluble solids portion, wherein the solids portion, including theprotein, is not subsequently subjected to an evaporator; and drying thesolids portion, including the protein, to define a grain meal thatincludes at least 40 wt % protein on a dry basis.
 10. The method ofclaim 9, after separating the whole stillage byproduct into an insolublesolids portion and a thin stillage portion, further comprisingseparating additional thin stillage from the insoluble solids portion.11. The method of claim 9 further comprising dewatering the solidsportion, including the protein, and drying the dewatered solids portion,including the protein, to define the grain meal that includes at least40 wt % protein on a dry basis.
 12. The method of claim 9, wherein theinsoluble solids portion defines a wet cake portion.
 13. A method forproducing a grain meal from a whole stillage byproduct comprising:separating the whole stillage byproduct into an insoluble solids portionand a thin stillage portion, which includes protein; prior to anyevaporation step, separating the thin stillage portion into only twostreams, with one stream including a solids portion, which includes theprotein, and the other stream including a liquid portion, wherein thesolids portion, including the protein, is not subsequently subjected toan evaporator; and drying the solids portion, including the protein, todefine a grain meal that includes at least 40 wt % protein on a drybasis.
 14. The method of claim 13 further comprising, after separatingthe whole stillage byproduct into an insoluble solids portion and a thinstillage portion, separating additional thin stillage from the insolublesolids portion.
 15. The method of claim 13 further comprising dewateringthe solids portion, including the protein and drying the dewateredsolids portion, including the protein, to define the grain meal thatincludes at least 40 wt % protein on a dry basis.
 16. The method ofclaim 13, wherein the insoluble solids portion defines a wet cakeportion.
 17. A method for producing a grain meal from a whole stillagebyproduct comprising: separating the whole stillage byproduct into aninsoluble solids portion and a thin stillage portion, which includesprotein; prior to any evaporation step, separating a solids portion,including the protein, from the thin stillage portion, wherein thesolids portion, including the protein, is not subsequently subjected toan evaporator; dewatering the solids portion, including the protein; anddrying the dewatered solids portion, including the protein, to define agrain meal that includes at least 40 wt % protein on a dry basis. 18.The method of claim 17 further comprising, after separating the wholestillage byproduct into an insoluble solids portion and a thin stillageportion, separating additional thin stillage from the insoluble solidsportion.
 19. The method of claim 17, wherein the insoluble solidsportion defines a wet cake portion.